Hydrostatic piston machine according to the floating cup concept

ABSTRACT

The invention relates to a hydrostatic piston engine ( 1 ) which is based on the floating cup principle and comprises a first swash plate ( 16 ) and as well as a second swash plate ( 17 ). A first cylinder drum unit ( 11, 14 ) rests against the first swash plate while a second cylinder drum unit ( 12, 15 ) leans on the second swash plate ( 17 ). A first group of pistons ( 10 ) and a second group of pistons ( 12 ) are connected in a fixed manner to a drive shaft ( 5 ) of the hydrostatic piston engine ( 1 ). The first group of pistons ( 10 ) engages into the cylinder cavities of the first cylinder drum unit ( 11, 14 ) while the pistons ( 12 ) of the second group engage into cylinder cavities of the second cylinder drum unit ( 12, 15 ). The first and second cylinder chambers embodied by the pistons ( 10, 12 ) and the cylinder drum units ( 11, 14; 12, 15 ) can be connected to a first hydraulic circuit and a second hydraulic circuit, respectively. The axis of rotation of the first cylinder drum units ( 11, 14 ) and/or the axis of rotation of the second cylinder drum unit ( 12, 15 ) can be adjusted independently of the axis of rotation of the other cylinder drum unit.

The invention relates to a hydrostatic piston machine according to the floating cup principle.

Hydrostatic piston machines according to the floating cup principle are improved with respect to conventional piston machines in terms of their friction losses. A piston machine of this kind, which works according to the floating cup principle, is known from WO 03/058035 A1. The hydrostatic piston machine has a driving shaft which is arranged in a housing, with an arrangement of pistons being rigidly connected to the driving shaft via a support plate. A respective drum plate, on which cylinders are arranged, is likewise connected to the driving shaft in a rotationally rigid manner for each group of the pistons projecting from the support plate in the opposite direction. The axis of rotation of the drum plates is inclined by the same degree in each case relative to the driving shaft axis, so that the pistons of the first group as well as of the second group which are arranged in the cylinders execute a reciprocating movement relative to the cylinders. Comparable forces in each case act on the pistons in the axial direction due to the inclination, which is the same in opposite directions, of the axes of rotation of the two drum plates.

The power transmission groups which are formed on both sides of the support plate by the respective pistons, cylinders and drum plates deliver into a common hydraulic circuit. The high pressure sides of the two drum units as well as the low pressure sides of the two drum units are connected to one another in the housing of the piston machine for this purpose. The two drum plates are in each case supported at a swash plate, with the swash plates being adjustable together.

The described hydrostatic piston machine entails the disadvantage of both groups of pistons only delivering into a common hydraulic circuit and the adjustment of the two swash plates corresponding with one another. A common adjustment of this kind of the two swash plates is required in the hydrostatic piston machine which is known from WO 03/058035 A1 in order to adapt the axial forces which act on the pistons of both groups to one another.

However it is not possible to use a piston machine of this kind in a hydraulic system which comprises two individual circuits which are to be supplied independently of one another. In this respect it is neither possible to use the hydrostatic piston machine to supply two separate hydraulic circuits, for example as a dual pump, nor is it possible to set a volumetric delivery individually in each case for the first group of pistons and the second group of pistons through an independent adjustment of the two swash plates.

The object of the invention is to provide a hydrostatic piston machine according to the floating cup principle in which a more flexible use is possible by isolating the delivery for the two power transmission groups.

The object is achieved by the hydrostatic piston machine according to the invention with the features of Claim 1 and the features of Claim 2, respectively.

The hydrostatic piston machine according to the invention has two power transmission groups. The first power transmission group comprises a first swash plate on which a first cylinder drum unit is supported. A first group of pistons is arranged in the cylinder recesses of the first cylinder drum unit, these pistons being connected to a driving shaft of the hydrostatic piston machine in a rotationally rigid manner. In a corresponding manner a second power transmission group comprises a second swash plate on which a second cylinder drum unit is supported. Cylinder recesses, in which a second group of pistons engage, are likewise arranged in this second cylinder drum unit. The second group of pistons is likewise connected to the driving shaft of the hydrostatic piston machine in a rotationally rigid manner. A first group of cylinder chambers is formed in the cylinder recesses of the first cylinder drum unit by the first group of pistons. A second group of cylinder recesses is accordingly also formed in the cylinder recesses of the second cylinder drum unit by the second group of pistons. The first group of cylinder chambers and the second group of cylinder chambers are in each case connected to an individual hydraulic circuit in order to obtain two delivery flows of pressure medium. As a result, the hydrostatic piston machine, which is formed as a hydraulic pump, for example, delivers through the first power transmission unit into a first working line and through the second power transmission unit into a second working line. The hydrostatic piston machine can therefore also be used for applications in which hydraulic circuits which are independent of one another are to be supplied.

The two power transmission groups of the hydrostatic piston machine according to the invention with the features of Claim 2 are independently adjusted. It is as a result possible, when the hydrostatic piston machine is used as a hydraulic pump, to firstly adjust the volumetric delivery through the first power transmission group. An adjustment in the same direction is then likewise carried out through the second power transmission groups, for example. An independent delivery rate setting when delivering into two hydraulic circuits is of particular advantage. In this case the mutually independent adjustment of the two power transmission groups also enables one group to be implemented with a constant swept volume and, on the other hand, the second power transmission group to be implemented so as to be adjustable. The first power transmission group is in this respect again formed by a cylinder drum unit as well as the cylinder recesses arranged at the latter together with the first group of pistons. The second power transmission group is accordingly formed by the second group of pistons together with the second cylinder recesses of the second cylinder drum unit. The adjustment takes place by changing the axis of rotation of the respective cylinder drum unit. The axis of rotation of the respective cylinder drum unit is in this respect changed independently of the orientation of the axis of rotation of the respective other cylinder drum unit. Although they can be changed independently of one another, the axes of rotation of the two cylinder drum units can be adjusted together, depending on the application.

Advantageous developments of the hydrostatic piston machine according to the invention are presented in the subclaims.

It is in particular of advantage, in order to individually adjust the pivoting angle of the cylinder drum units, to provide a respective swash plate which can be adjusted in two opposite directions from a neutral position. As a result, when delivering into at least two different hydraulic circuits, the delivery direction can be reversed in the two hydraulic circuits. This reversal of the delivery direction may also take place in a mutually independent manner. In this respect the neutral position does not necessarily have to coincide with a running surface of the swash plates which is perpendicular to the driving shaft axis. A small angle, which compensates for hydraulic losses, between the normals to the surfaces of the swash plate and the driving shaft may also define a neutral position.

It is also of advantage to set the swash plates by means of an adjusting device which executes a linear actuating movement. A slender construction of the entire unit can be obtained through an actuating device with a linear actuating movement. It is in particular easily possible to obtain a linear actuating movement of this kind by means of an adjusting piston which is hydraulically loaded. It is in this respect of particular advantage for the linear actuating movement to be executed parallel to the driving shaft axis. A linear actuating movement of this kind executed parallel to the driving shaft axis enables the adjusting device to be arranged parallel relative to the driving shaft axis.

The pressure medium supply and pressure medium removal to and from the first and second cylinder chambers is preferably effected through the swash plate. Pressure medium channels are made in the swash plate for this purpose. The pressure medium channels of the first and of the second swash plate, respectively, preferably lead into a channel portion of a first and second housing flange part, respectively. Hydrostatic relief of the swash plate can also advantageously be effected through this arrangement. For this purpose leakage fluid which escapes upon passing from the pressure medium channels of the swash plates to the channel portions of the first and second housing flange part, respectively, is used to form a hydrodynamic mounting between the swash plates and the corresponding first bearing surface of the first housing flange part and the second corresponding bearing surface of the second housing flange part, respectively. The first and the second swash plate are therefore arranged such that they can pivot in a sliding manner in the first housing flange part and second housing flange part, respectively, and hydrostatically relieved by way of a small leakage quantity of pressure medium. There is therefore no need for a special pressure medium supply in order to lubricate the mounting of the swash plates.

At least one of the working connections, which can be connected via the pressure medium channels in the first and the second swash plate, respectively, to the first cylinder chambers and the second cylinder chambers, respectively, is formed at the first housing flange part and the second housing flange part, respectively. The connection is therefore routed to the outside over a short path inside the hydrostatic piston machine. Each of the working connections is connected to a feed valve unit, via which not only is pressure medium post-fed, but which also has a high pressure limiting valve for safeguarding the connected working line.

It is also of advantage to provide a common feed pressure channel in the first housing flange part, a further housing part and the second housing flange part. The feed valve units are supplied with the pressure medium which is to be post-delivered via this common feed pressure channel. The common feed pressure channel has the advantage of a central connection being sufficient to post-deliver pressure medium for feeding by means of a fixed displacement pump, for example. As a result of using just one common connection, there is no need for additional sealing points, and the expenditure for installing lines at the hydrostatic piston machine is reduced.

A preferred embodiment of the hydrostatic piston machine according to the invention is represented in the drawings and illustrated in detail on the basis of the following description. In the drawings:

FIG. 1 is a first perspective representation of a hydrostatic piston machine according to the invention;

FIG. 2 is a second perspective representation with a partial section through an adjusting device of the hydrostatic piston machine according to the invention;

FIG. 3 is an external view of a hydrostatic piston machine according to the invention;

FIG. 4 is a second external view of a hydrostatic piston machine according to the invention with a partial section through an adjusting device;

FIG. 5 is a further perspective representation of the piston machine according to the invention;

FIG. 6 is a first schematic representation of a first housing flange part in a perspective view;

FIG. 7 is a second schematic representation of the first housing flange part;

FIG. 8 is a third schematic representation of a first housing flange part of the hydrostatic piston machine according to the invention; and

FIG. 9 is a fourth schematic representation of a hydrostatic piston machine according to the invention.

A perspective representation of a hydrostatic piston machine 1 according to the invention is represented in FIG. 1. The hydrostatic piston machine 1 has a housing which comprises a first housing flange part 2 and a second housing flange part 3. The first housing flange part 2 and the second housing flange part 3 are arranged at two opposite sides at a substantially tubular further housing part 4 and complete this to form a closed housing. A driving shaft 5 is rotatably mounted in the housing of the hydrostatic piston machine 1. A first bearing 6 is arranged in the first housing flange part 2 and a second bearing 7 is arranged in the second housing flange part 3 in order to rotatably mount the driving shaft 5. The first bearing 6 and the second bearing 7 are preferably constructed as rolling contact bearings.

In order to connect the first housing flange part 2 and the second housing flange part 3 to the further housing part 4, the individual parts of the housing are connected to one another by way of screws 8.

A support plate 9 is connected to the driving shaft 5 in a rotationally rigid manner. The support plate 9 is of disc-shaped construction and arranged approximately centrally in the region of the further housing part 4. A first group of pistons 10 extends out from the support plate 9 in the direction of the first housing flange part 2. The pistons 10, only one of which is given a reference number for the sake of clarity, are arranged on a common circumferential circle on the support plate 9. On their side which is remote from the support plate 9 the pistons 9 engage in a respective cylinder recess of a cylinder 11, these being arranged on a drum plate 14. Together with the first drum plate 14 and the first group of cylinders 11, the first group of pistons 10 forms a first power transmission group.

A second group of pistons 12 is arranged at the surface of the support plate 9 which is oriented in the opposite direction, which pistons can likewise engage by way of their side which is remote from the support plate 9 in cylinder recesses of a corresponding group of cylinders 13 and also be staggered relative to the pistons 11 of the first group 11. FIG. 1 shows the opposite arrangement, in which a through-hole can be punched in the support plate 9. The second group of cylinders 13 is arranged on a second drum plate 15. A second power transmission group is therefore formed on the opposite side of the support plate 9. The first group of cylinders 11 is rigidly fixed to the first drum plate 14 and the second group of cylinders 13 is rigidly fixed to the second drum plate 15 solely in the axial direction, i.e. a lateral movement on the respective drum plate 14 and 15 is possible. For this purpose the cylinders 11 and 13 are fixed in the axial direction in a manner which is not represented. However the cylinders 11 and 13, respectively, can execute a sliding movement on the supporting surface, which cannot be discerned, of the first drum plate 14 and the supporting surface 15′, which is visible in FIG. 1, of the second drum plate 15, respectively. If the first drum plate 14 and the second drum plate 15 are inclined relative to the driving shaft 5, the elliptical projection of the pistons 10 and 12 onto the first supporting surface, which is not represented, of the first support plate 14 and the second supporting surface 15′ of the second support plate 15 is therefore compensated when a rotational movement is executed.

A spherical formation may also be provided instead of the plane supporting surfaces and cylinder bottoms. The compensating movement is then linked with a tilting movement of the cylinders 11, 13.

In order to incline the first drum plate 14 or the second drum plate 15, the first drum plate 14 is supported at a first running surface, which cannot be discerned in FIG. 1, of a first swash plate 16. The second support plate 15 is accordingly supported at a second running surface 18 of a second swash plate 17. The first swash plate 16 and the second swash plate 17 can be set independently of one another in terms of their angle relative to the driving shaft 5. The axes of rotation of the drum plates 14, 15 lying against the running surfaces and therefore all the cylinder drum units are consequently fixed independently of one another through the swash plates 16, 17. The first drum plate 14 and the second drum plate 15 are connected to the driving shaft 5 in a rotationally rigid manner, so that the side of the first drum plate 14 which is remote from the first group of cylinders 11 rotates in a sliding manner on the running surface of the first pivoting plate 16. The second drum plate 15 is connected to the driving shaft 5 in a corresponding rotationally rigid manner and rotates on the running surface 18 of the second swash plate 17.

The pistons 10 of the first and the pistons 12 of the second group, respectively, execute a reciprocating movement in the first cylinders 11 and the second cylinders 13, respectively, through the angles, set by way of the first swash plate 19 and the second swash plate 17, of the axes of rotation of the first drum plate 14 and the second drum plate 15, respectively, relative to the driving shaft 5.

In order to enable the pivoting angle of the first swash plate 16 to be set, the first swash plate 16 is constructed as a pivoting rocker and a sliding surface 19 is formed at the first swash plate 16 on the side which is remote from the running surface which is not represented. In a corresponding manner the second swash plate 17 is constructed as a pivoting rocker and a second sliding surface 20 is formed at the second swash plate 17 on the side which is remote from the running surface 18 of the second swash plate 17. The first sliding surface 19 and the second sliding surface 20 form a sliding contact bearing with corresponding bearing surfaces of the first housing flange part 2 and the second housing flange part 3, respectively, as is yet to be described.

A central recess, which is preferably elliptical, is in each case provided in the swash plates 16, 17 in the same way as in the drum plates 14, 15 for the passage of the driving shaft 5.

In order to connect the first cylinder chambers to a first hydraulic circuit, the first cylinder chambers are alternately connected to a high pressure and low pressure connection. For this purpose an opening is provided in the cylinders bottoms, supported at the first drum plate 14, of the first cylinders 11 as well as in the first drum plate 14 for each cylinder 11. These openings are connected in succession to control openings arranged in the running surface of the first swash plate 16 during a rotation of the first drum plate 14 together with the first cylinders 11 on the running surface of the first swash plate 16. The control openings are mouths of pressure medium channels which are formed in the first swash plate 16. The pressure medium channels therefore connect the running surface of the first swash plate 16 to the first sliding surface 19, which is oriented in the opposite direction, of the first swash plate 16. The mouths of the pressure medium channels on the side of the first sliding surface 19 are formed such that there is a connection to the low pressure or high pressure connection of the first housing flange part 2 irrespective of the pivoting angle of the first swash plate 16 which is set in each case. In addition to the standard-shaped control openings, notches or bores can be made in the running surface of the first swash plate in order to improve the reversing behaviour, for example in order to reduce pulsations.

In a corresponding manner two pressure medium channels are formed in the second swash plate 17, these forming control openings on the side of the running surface 18. The pressure medium channels likewise open at the second sliding surface 20, which is oriented in the opposite direction, such that, with corresponding openings which are formed in the second flange part 3, they form a permanent connection, irrespective of the pivoting angle of the swash plate 17 which is set.

An adjusting device 21, which co-operates with the second swash plate 17, is represented in FIG. 1. The adjusting device 21 preferably executes a linear actuating movement, which is described subsequently with reference to FIG. 2. The adjusting device 21 is arranged on the outside of the further housing part 4 and oriented substantially parallel to the driving shaft 5. The adjusting device 21 which is oriented in parallel co-operates via a sliding block and an actuating lever 47 with the second swash plate 17 and adjusts the inclination of the running surface 18 relative to the driving shaft 5 by means of a linear movement. The adjustment can take place in both directions. The normal to the surface of the running surface 18 coincides with the axis of the driving shaft 5 in a neutral position, for example. The second swash plate 17 can be pivoted out of this neutral position in the direction of positive as well as in the direction of negative angles. The delivery direction of the second power transmission group can thus be reversed.

The hydrostatic piston machine according to the invention is intended for delivery into two separate hydraulic circuits. The first cylinder drum unit together with the first piston 10 is in this respect connected to a first hydraulic circuit via a first working line connection 22 and a second working line connection 23. The first working line connection 22 and the second working line connection 23 are arranged in the first housing flange part 2 and connect the control kidneys of the first swash plate 10 via a first working line channel 24 and a second working line channel 25, respectively, to working lines.

In a corresponding manner the control kidneys of the second swash plate 17 are connected via a third working line connection 26 and a fourth working line connection 28 to a second hydraulic circuit. The second hydraulic circuit is likewise formed as a closed circuit, with a third working line channel 27 and a fourth working line channel 29 being provided for pressure medium supply in the second housing flange part 3. The third working line channel 27 and the fourth working line channel 29 connect the third working line connection 26 and the fourth working line connection 28 via the pressure medium channels provided in the second swash plate 17 to the respective control kidneys in the running surface 18 of the second swash plate 17.

On account of the independent adjustment of the first swash plate 16 and the second swash plate 17, which can both be pivoted out of their respective neutral position in two opposite directions, it is also possible to select the delivery directions in the first hydraulic circuit and in the second hydraulic circuit independently of one another. A further adjusting device, which is arranged on the back, which cannot be discerned in FIG. 1, of the hydrostatic piston machine 1 is provided to adjust the first swash plate 16. The neutral position of the first swash plate 16, just like that of the second swash plate 17, does not necessarily correspond to the position in which the running surfaces of the first swash plate 16 and the second swash plate 17 form a right angle with the driving shaft 5. It is in particular also possible for the neutral position of the first swash plate 16 to form a different angle relative to the axis of the driving shaft 5 than the neutral position of the second swash plate 17.

A common feed system is provided in order to post-deliver pressure medium into the first hydraulic circuit and the second hydraulic circuit as well as to safeguard the hydraulic circuits with respect to high working pressures. The first working line channel 24 is connected to a feed valve unit, which is not visible in FIG. 1. The second working line channel 25 is accordingly connected to a second feed valve unit 30. The first working line channel 24 as well as the second working line channel 25 can be connected via the first feed valve unit and the second feed valve unit 30 to a first connecting channel 32. A respective non-return valve, which opens in the direction of the working line connection 22 and 23, respectively, is provided in the feed valve units, with a high pressure limiting valve being arranged parallel to this non-return valve. In the event of a critically high pressure acting in the closing direction of the non-return valve, the non-return valve can be bypassed by means of the high pressure limiting valve, thus relieving the corresponding working line in the direction of the first connecting line 32.

In a corresponding manner the third working line channel 27 and the fourth working line channel 29 are connected via a third and fourth feed valve unit 31, respectively, to a second connecting channel 33. The first connecting channel 32 and the second connecting channel 33 open at a feed pressure limiting valve 34, via which the first connecting channel 32 and the second connecting channel 33 can be relieved into a tank volume if a certain feed pressure fixed by a spring is exceeded. The tank volume may, for example, be identical to the internal housing volume of the hydrostatic piston machine 1, in which case the pressure medium collected in the internal tank volume of the hydrostatic piston machine 1 is removed in a manner which is not represented via a return line to a further, external tank volume.

A feed line connection 35 is provided in order to post-deliver pressure medium, via which connection a feed pressure which is generated by an auxiliary pump is supplied to the first connecting channel 32 and the second connecting channel 33. The auxiliary pump may, for example, be a fixed displacement pump with through-drive which is arranged in the first or second housing flange part 2, 3. The corresponding housing flange part 2, 3 has an intake connection in order to enable pressure medium to be drawn in from a tank volume. The connecting channel 32, 33 is formed in an overlapping manner in the further housing part 4 as well as in the first housing flange part 2 and the second housing flange part 3. The feed line connection 35 as well as the feed pressure limiting valve 34 are arranged in the further housing part 4 and jointly take over the pressure limiting function in the feed system for the feed valve units of the first housing flange part 2 as well as the feed valve units of the second housing flange part 3.

Pressure medium is in each case post-fed on the low pressure side through the feed valve units 30, 31 associated with the working line channel 24, 25, 27 and 29, respectively, if the pressure in the working line carrying the low pressure is below the feed pressure.

A part-sectional representation of the hydrostatic piston machine according to the invention of FIG. 1 is represented in FIG. 2. It can be seen in the section through the adjusting device 21 that a first stop 37 and a second stop 38 are formed at a guide rod 36. A first spring hanger 39 and a second spring hanger 40 are arranged in a sliding manner on the guide rod 36 between the first stop 37 and the second stop 38. A compression spring 41, which in the represented embodiment is formed as a spiral spring, is arranged between the first spring hanger 39 and the second spring hanger 40. The first spring hanger 39 and the second spring hanger 40 are arranged so as to be displaceable with their outer circumference in a recess of an adjusting piston 42.

A deflection of the adjusting piston 42 to the right is represented in FIG. 2. A driving device is provided in the recess of the adjusting piston 42, at which device the first spring hanger 39 is supported and therefore follows the movement of the adjusting piston 42 to the right. The compression spring 31, which is supported at the second spring hanger 38 at the second stop 38 of the guide rod 36, is then compressed. If a movement takes place in the opposite direction, the spring 41 is supported via the first spring hanger 39 at the adjusting piston 42 until the first spring hanger 39 is in contact with the stop 37. Further movement of the adjusting piston 42 to the left causes the second spring retainer 40 to be driven via a driving device, which cannot be discerned in FIG. 2, of the adjusting piston 42 to the left, so that the spring 41 is now compressed on account of the contact with the first stop 37 as well as the second driving device of the adjusting piston 42.

A first actuating pressure chamber 43 and a second actuating pressure chamber 44 are provided in order to deflect the adjusting piston 42 out of its rest position, which is defined by the spring 41. The actuating pressure chambers 43 and 44 are formed between an outer circumference of the adjusting piston 42 and a housing portion 4′ of the adjusting device 21 which is formed at the further housing part 4. In order to generate an axial hydraulic force on the adjusting piston 40, a radially widened region is formed at the adjusting piston 42, which region separates the two actuating pressure chambers 43 and 44 from one another and forms in each actuating pressure chamber 43, 44 a surface which can be loaded by the actuating pressure. A sliding block 46, which co-operates with the actuating lever 47, is formed at the adjusting piston 42 at the end of the adjusting piston 42 which is remote from the guide rod 36. The actuating lever 47 is rigidly connected to the second swash plate 17, so that a linear movement of the sliding block 46 gives rise to a rotational movement of the second swash plate 17. In order to change the actuating pressures in the actuating pressure chambers 43 and 44, which act in opposition, a pilot valve, for example, is used in a manner which is known per se, which valve is connected in a manner which is not represented to the first actuating pressure chamber 43 and the second actuating pressure chamber 44.

An external view of the hydrostatic piston machine 1 according to the invention is once again represented in FIG. 3. The adjusting device 21 is arranged in a region of the further housing part 4. Here the guide rod 36 projects out of a cover portion 48 which is preferably arranged at the first housing flange part 2. The guide rod 36 is preferably fixed by way of a thread in the cover portion 48, so that the axial position of the guide rod 36 and therefore the neutral position of the second swash plate 17 can be set by rotating the guide rod 36. A lock nut 49 serves to fix the axial position.

A partial section through a hydrostatic piston machine according to the invention is once again shown in FIG. 4. It can be seen here that a housing portion 4′ for the adjusting device 21 is formed in the further housing part 4, which is closed on both sides by the first housing flange part 2 and the second housing flange part 3. This housing portion 4′ is closed on one side by a first cover portion 48 and on the opposite side by a second cover portion 50 of the second housing flange part 3. The second cover portion 50 accommodates the region of the sliding block 46 and of the actuating lever 47.

In the further view which is represented in FIG. 5 the two further feed valve units 51 and 52 can be seen in addition to the feed valve units 30, 31 which are already known from FIGS. 1 and 2. Moreover, corresponding to the arrangement of the adjusting device 21 for the second swash plate 17, a further adjusting device 53 is provided, this co-operating with the first swash plate 16 and being arranged in a housing portion lying opposite the housing portion 4′ at the further housing part 4. The further adjusting device 53 for the first swash plate 16 corresponds in its structure to the described adjusting device 21. A cover portion 55 is provided at the first housing flange part 2 in order to accommodate the sliding block of the further adjusting device 53. The first connecting channel 32 consists of a first portion 32 a and a second portion 32 b which are formed in the further housing part 4 and the first housing flange part 2, respectively. The second connecting channel 33 accordingly consists of a first portion 33 a formed in the further housing part 4 and a second portion 33 b in the second housing flange part 3. In order to post-deliver pressure medium into the first working line channel 24 and the second working line channel 25, respectively, the second portion 32 b of the first connecting channel 32 branches into a first channel portion 32′ and a second channel portion 32″.

The second portion 33 b of the second connecting channel 33 accordingly branches into a third channel portion 33′ and a fourth channel portion 33″.

Here the branching of the first connecting channel 32 and the second connecting channel 33, respectively, is formed in the first housing flange part 2 and the second housing flange part 3, respectively. This means that only one channel mouth has to be sealed in each case upon passing from the further housing part 4 to the first housing flange part 2 or the second housing flange part 3.

The first housing flange part 2 is represented in FIG. 6. It can be seen that a bearing surface 60′, 60″ is formed in the first housing flange part 2, which surface corresponds to the curvature of the first sliding surface of the first swash plate 16. The first working line channel 24 and the second working line channel 25 open in a first opening 24′ and a second opening 25′, respectively, in the bearing surface 60′, 60″. In this case the dimensions of the first opening 24′ and the second opening 25′ are preferably identical for a hydrostatic piston machine 1 with reversible control. The first opening 24′ and the second opening 25′ preferably extend along a portion of the bearing surface 60′, 60″. The leakage fluid arising upon passing from the mouths of the pressure medium channels of the first swash plate 16 at the sliding surface 19 to the first working line channel 24 and the second working line channel 25, respectively, serves to form a lubricating film on the bearing surface 60, 60′. The first swash plate 16, which is rotatably mounted in the bearing surface 60′, 60″, is lubricated by the lubricating film on the bearing surface 60′, 60″. Recessed regions 62 a, 62 b, 62 c are formed next to the bearing surfaces 60′, 60″, which regions accommodate the leakage fluid and provide hydrostatic relief. Lateral walls seal the recessed regions 62 a, 62 b, 62 c with respect to the swash plate 16.

FIG. 7 shows a further representation of a first housing flange part 1 in a slightly amended perspective. The formation of the second housing flange part 3 corresponds to the first housing flange part 2.

The first housing flange part 2 is represented in a turned view in FIG. 8. It can be seen in this view that a cover portion 55 is formed at the first housing flange part 2, in which portion a recess 61 is provided for accommodating the actuating lever 47 as well as the sliding block 46 of the adjusting piston 42.

FIG. 9 shows a further representation of the first flange part 2.

The invention is not tied to the represented embodiment. The individual features which are shown in the represented embodiment can in particular be combined with one another in any desired way. 

1. Hydrostatic piston machine with a first swash plate on which a first cylinder drum unit is supported, in the cylinder recesses of which unit a first group of pistons is arranged, and with a second swash plate on which a second cylinder drum unit is supported, in the cylinder recesses of which unit a second group of pistons is arranged, wherein the pistons of the first group and the pistons of the second group are connected to a driving shaft of the hydrostatic piston machine in a rotationally rigid manner, wherein first cylinder chambers which are formed between the cylinder recesses of the first cylinder drum unit and the pistons of the first group can be connected to a first hydraulic circuit, and that second cylinder chambers which are formed between the cylinder recesses of the second cylinder drum unit and the pistons of the second group can be connected to a second hydraulic circuit.
 2. Hydrostatic piston machine with a first swash plate on which a first cylinder drum unit is supported, in the cylinder recesses of which unit a first group of pistons is arranged, and with a second swash plate on which a second cylinder drum unit is supported, in the cylinder recesses of which unit a second group of pistons is arranged, wherein the pistons of the first group and the pistons of the second group are connected to a driving shaft of the hydrostatic piston machine in a rotationally rigid manner, wherein a first axis of rotation of the first cylinder drum unit and/or a second axis of rotation of the second cylinder drum unit can be adjusted independently of the axis of rotation of the respective other cylinder drum unit.
 3. Hydrostatic piston machine according to claim 1 or 2, wherein a respective swash plate, which can be adjusted in two opposite directions from its respective neutral position, is provided in order to adjust the first axis of rotation of the first cylinder drum unit and/or the second axis of rotation of the second cylinder drum unit.
 4. Hydrostatic piston machine according to claim 1 or 2, wherein each swash plate co-operates with an adjusting device which executes a linear actuating movement.
 5. Hydrostatic piston machine according to claim 4, wherein the linear actuating movement can be executed parallel to the driving shaft.
 6. Hydrostatic piston machine according to claim 1 or 2, wherein pressure medium channels are arranged in the respective first and second swash plate in order to connect first cylinder chambers defined by the first cylinder drum unit with the first group of pistons and second cylinder chambers defined by the second cylinder drum unit with the second group of pistons to one or a plurality of hydraulic circuit(s).
 7. Hydrostatic piston machine according to claim 6, wherein at least one respective pressure medium channel of the first and of the second swash plate, respectively, opens into a working line channel of a first and second housing flange part, respectively.
 8. Hydrostatic piston machine according to claim 6, wherein the first swash plate is mounted in a hydrostatically relieved manner in a first housing flange part and the second swash plate is mounted in a hydrostatically relieved manner in a second housing flange part.
 9. Hydrostatic piston machine according to claim 8, wherein the first swash plate is mounted in a sliding manner on a corresponding first bearing surface in the first housing flange part and the second swash plate is mounted in a sliding manner on a corresponding second sliding surface in the second housing flange part.
 10. Hydrostatic piston machine according to claim 6, wherein at least one working line connection is in each case provided in the first housing flange part and in the second housing flange part and connected to the working line connections of a respective feed valve unit.
 11. Hydrostatic piston machine according to claim 10, wherein the at least one working line connection of the first housing flange part and the at least one working line connection of the second housing flange part are arranged towards one side of the hydrostatic piston machine.
 12. Hydrostatic piston machine according to claim 6, wherein the driving shaft is mounted at least by means of a first driving shaft bearing in the first housing flange part and by means of a second driving shaft bearing in the second housing flange part.
 13. Hydrostatic piston machine according to claim 1 or 2, wherein the hydrostatic piston machine comprises a first housing flange part, a second housing flange part and at least one further housing part, to which the first and the second housing flange part are connected.
 14. Hydrostatic piston machine according to claim 11, wherein a common feed pressure channel is arranged in the first housing flange part, the second housing flange part and the at least one further housing part. 